The present invention generally relates to a method and system for monitoring an electromagnetic switching device, and to an electromagnetic switching device itself. More particularly, it can include a method at least for the correct connection of an input contact and of an output contact using a contact bridge. The contact bridge can be moved from a separated position into a connection position using a bridge drive when a connection command is given, if the contacts are correctly connected. The electromagnetic switching device can include circuit breakers, relays, etc.
Electromagnetic switching devices, including circuit breakers and relays, are generally known. They exhibit at least one input contact and one output contact which are connected to one another or separated from one another via a contact bridge. Apart from normal wear, two types of disturbances can essentially occur. One disturbance is the breaking of the contact bridge. In this case, the contacts can no longer be correctly connected to one another. The other disturbance is that the contact bridge becomes welded to the contacts. In this case, the contacts can no longer be correctly separated from one another. A broken bridge, in particular, can lead to the destruction of the entire electromagnetic switching device and also to disturbances in a connected installation.
Naturally, it is possible to check the electromagnetic switching device for correct functioning in a test circuit. However, this test is done in a test circuit. Continuous monitoring of the electromagnetic switching device during its operation is not possible by this means.
An object of an embodiment of the present invention includes creating a monitoring method for an electromagnetic switching device (including circuit breakers, relays, etc.) and an electromagnetic switching device corresponding thereto, via which the electromagnetic switching device can be monitored at least for a correct connection of the contacts in continuous operation.
An object can be achieved for the monitoring method in that when the connection command is given, a monitoring circuit is coupled to the contacts before the contact bridge is moved into the connection position. An indicator of the correct connection of the contacts can be determined by evaluating a contact voltage which is dropped across the contacts and which is supplied to the monitoring circuit.
Correspondingly, an object with respect to the electromagnetic switching device can be achieved in that
a monitoring circuit can be coupled to the contacts via an auxiliary switch,
the auxiliary switch can be constructed in such a manner that when a connection command is given, the auxiliary switch is closed-before the contact bridge is moved into the connection position, and
the monitoring circuit can deliver an indicator of the correct connection of the contacts.
If the contact bridge is moved from the connection position into the separated position using the bridge drive when a separating command is given when the contacts are correctly separated, the monitoring circuit is decoupled from at least one of the contacts after the contact bridge has been moved into the separated position when a separating command is given. An indicator of the correct separation of the contacts can then be determined by evaluation of the contact voltage. The electromagnetic switching device can also be monitored for correct separation of the input contact from the output contact by the contact bridge.
If the contact voltage is rectified before it is supplied to the monitoring circuit, the monitoring circuit can be used independently of the type and possibly polarization of the switched voltage.
If a preliminary signal corresponding to the contact voltage is supplied to an evaluating unit which determines the indicator, the determination of the indicator can be particularly simple.
If the preliminary signal is supplied to the evaluating unit in a DC-isolated manner, the evaluating unit can be incorporated in a particularly simple manner into a higher-level controller and/or the circuit breaker controller. In particular, it is possible to move the electromagnetic switching device into a safe state if the contacts are incorrectly connected or separated, respectively. As an alternative or additionally, it is possible to signal the incorrect connection or separation of the contacts to a higher-level controller if the contacts are not correctly connected or separated, respectively.